In recent years, premiumisation and quality improvement of vehicles leads, from the view point of occupant's comfort and environmental considerations, desire to various noise reductions, in particular pass-by noise.
When a contacting element on a tread of a tire enters to or exits from a contact patch during rolling, the tread is forced to be bent due to flattening. At this stage, geometrical discontinuity caused by periodical contact of relatively axial grooves to the contact patch leads inhomogeneity of a bending stiffness of the tread in a circumferential direction and excites internal construction of the tire to generate noise.
In order to reduce such inhomogeneity of the bending stiffness of the tread in a circumferential direction, it is known that reduction of a volume of the axial groove is effective. However, it is also known that reduction of the volume of the axial groove penalizes hydroplaning performance of the tread. Thus, it is desired to improve noise performance while maintaining hydroplaning performance.
The applicants have proposed in FIG. 1 of an international patent application PCT/JP2015/086150, a pneumatic tire tread having a connecting member connecting a transverse face of a contacting element to a transverse face of a circumferentially adjacent contacting element and being made of a material having a higher Young modulus than a Young modulus of a contacting element to obtain satisfactory hydroplaning performance and satisfactory noise performance at the same time. In FIG. 6, is disclosed a pneumatic tire tread having a connecting member connecting a transverse face of a contacting element to a transverse face of circumferentially adjacent contacting element and extending continuously through two transverse faces of the same contacting element for improving productivity of such tread.
However, embedding such connecting member in the contacting element so as to connect two side faces of adjacent contacting elements across the groove requires complicated manufacturing process, thus improvement of productivity of such tread is still insufficient.
EP0858875A1 discloses, in FIG. 1, a mold having a first die and a second die functionally adapted to form at least one orifice allowing a rubber passing through the orifice during molding. However with such configuration, it is difficult to remove the first die or the second die which forms a bottom of a groove or an incision in particular in a form of a tire, thus a complicated process for removing such die is still required.
KR20130078562A discloses, in FIGS. 3 to 5, a method and a mold for manufacturing a pneumatic tire having a reinforced cord crossing a groove using a reinforced cord insertion block installed in a mold. However with such configuration, it is difficult to give a movement to the reinforced cord insertion block, necessary to place the reinforced cord into the reinforced cord insertion block thus a complicated process is still required, and moreover difficult to prevent rubber from flashing into the groove.
US20080152744A1 discloses, in FIG. 1, a molding element suitable for molding sunken grooves or sipes in a tread, and such device may be comprised of a thin flexible wire. However, with such molding element it is difficult to place a connecting member as to connect side faces of different contacting elements as the thin flexible wire is pulled out from the tread.
A “tire” means all types of elastic tire whether or not subjected to an internal pressure.
A “green tire” means a superposition of a plurality of semi-finished rubber products present in the form of strips or sheets, with or without reinforcement. The green tire is intended to be vulcanized in a mold in order to obtain the tire.
A “tread” of a tire means a quantity of rubber material bounded by lateral surfaces and by two main surfaces one of which is intended to come into contact with ground when the tire is rolling.
A “mold” means a collection of separate molding elements which, when brought closer towards one another, delimit a toroidal molding space.
A “molding element” of a mold means part of a mold. A molding element is, for example, a mold segment.
A “molding surface” of a molding element means a surface of the mold that is intended to mold a surface of the tread.
A “modulus at 10% elongation” is a tensile stress (in MPa) at ten percent (10%) elongation measured according to ASTM standard D412.
A “groove” is a space between two rubber faces/sidewalls which do not contact between themselves under usual rolling condition connected by another rubber face/bottom. A groove has a width and a depth.
It is thus an object of the disclosure to provide a molding element for a mold used for manufacturing a tread of a tire, such molding element can improve productivity for manufacturing a tread provided with a connecting member connecting two side faces of adjacent contacting elements.